I have given more thought to changing to a MP. I well realize that the additional speed is a relatively small matter for most everyday PS tasks, even though I work with large files and do much panoramic stitching, something that demands a lot of processing power. During a good part of generating a large panorama consisting of 5-7 30 Meg files, the performance monitor shows that all four threads are maxed out, and most of the machine's 4 gigs of RAM are in use.
I mind that Adobe is rumored to be coming out with an update that will make use of quad cores on dual processors. That may change the equation a bit. It is also important the realize that there is some point at which more machine power will make scant difference in actual throughput of work. As it is, most of our computers spend a lot more time waiting for us than we spend waiting for them.
But as you all know, raw speed is only a part of what makes for a desirable computer, and not always the biggest part. The OSX is a well evolved OS and the limited experience I've had using MAC's made me think they were very reliable and stable. I took a two week work shop at Anderson Ranch Art Center where about a dozen Power MAC's were used day and part of the night for two weeks without a reboot, hang, or anything from the machine that caused a work stoppage. That really impressed me. I was sometimes frustrated when attempting basic tasks that are easy for me in Windows because I know Windows very well, having used it daily since 3.1. I realize that it would not take me long to learn how to do everything I need to do on a MAC, but still, that is a small factor to consider.
I am in the process of selling one house and buying another, so I am putting the MAC decision on hold until we are settled in our new home. In the meantime I may buy some additional RAM for my 380, taking it to 8 gigs. That way, PS can have all it wants and there will be plenty of memory left for Windows and other applications.
Finally, thank you for the responses to my post,
Joe Stephenson